This invention relates to non-woven material containing wool, especially insulating material for clothing and bedding products, and in a particular aspect provides an insulating material formed predominantly from wool fibres.
Down is presently recognized as the superior lightweight filling for clothing and bedding products due to its excellent loftiness. High quality down has a volume fraction of 0.003, that is it contains only 0.3% fibre and 99.7% air by volume. This large volume of trapped, still air is vital to the excellent insulating properties of down and its high warmth to weight ratio. A second important characteristic of down is its high resilience, that is its ability to maintain excellent loft after repeated compressions and indeed through years of use.
A currently used synthetic substitute for down is a lightweight non-woven open web of polyester fibres. The web may be a conventional card web in which the fibres are partially aligned parallel to the web direction, or a random web in which there is no preferred orientation of the fibres. The resilience of the random web is considered to be superior to that of the partially aligned web. The open web structure is normally stabilized by some form of bonding. This bonding can be achieved by a variety of methods including chemical bonding methods and thermal bonding. A common form of chemical bonding is the use of either a spray adhesive (spray bonding) or bath immersion of the product in a solution of adhesive. Thermal bonding is a technique that appears to have a promising future and the non-woven industry has shown a trend towards this method. In thermal bonding, effective dispersed bonds are achieved by initially forming the web to include a portion of thermoplastic fibres of lower melting point than the majority of the polyester fibres. On heating the blend, the low melting point fibres melt to form droplets which on cooling bond and stabilise the structure. In a variation, the bonding is achieved using conjugate thermoplastic fibres, for example bicomponent fibres each in two parts, core and sheath, made from two different polymers of differing melting points. On heating, only one component melts and so the binder fibre maintains its integrity as a fibre rather than forming a droplet.
It is known that the properties of synthetic fibres may be enhanced in certain respects, by blending in a selected proportion of a staple natural fibre, such as wool. In particular, wool provides good moisture absorption capacity and therefore enhanced comfort for the user. A blended synthetic and wool insulating batt has been proposed in a paper by Hoffmeyer and Watt in WRONZ Report R128, January 1986, published by the Wool Research Organization of New Zealand (WRONZ). Various different lofty batts were formed as non-woven webs stablised by thermal bonding using a blend with mono or bicomponent bondable fibres and wool. Hoffmeyer and Watt reported that none of the fibres assessed gave a measurable bond to wool fibres, even when the latter had been pretreated by either scouring, solvent extraction, chlorination with 2.8% BASOLAN DC or chlorine-HERCOSETT treated with 2.8% BASOLAN DC followed by 2.8% HERCOSETT 57. Some of the webs at least mechanically trapped the wool fibres. The products were, however, observed to be poorly stabilised insofar as the wool fibres were concerned and to exhibit poor resilience and generally inferior properties relative to down.
A non-woven fabric comprised of thermoplastic fibres and wool fibres is disclosed in Australian patent 459539, wherein the wool fibres are said not to be interbonded to each other at their crossing points and only lightly bonded if at all at the points at which they cross the thermoplastic fibres, being held in the structure by mechanical constraint.